For your dry cough, a sugar-free dextromethorphan medication is safe. Avoid decongestants (like pseudoephedrine), as they can raise blood pressure and blood sugar. For your lip sores, a topical antiviral cream like acyclovir is safe to use. Additionally, please note that certain blood pressure medications (specifically ACE inhibitors) can actually cause a dry cough as a side effect. Do not stop your daily prescriptions, but do consult your doctor to review your medications, verify the cause of your cough, and ensure your blood sugar remains stable.